Can a person who comes to the US from Vietnam on a tourist visa successfully apply for refugee / asylum ? A friend of mine can come to the US on a tourist visa, and would like to stay in the US as a refugee. Is this possible? Good chances? Any thoughts would be appreciated.

Can a person who comes to the US from Vietnam on a tourist visa successfully apply for refugee / asylum ? A friend of mine can come to the US on a tourist visa, and would like to stay in the US as a refugee. Is this possible? Good chances? Any thoughts would be appreciated.